When I met Green Mountain Coffee's founder Robert Stiller in 2001, he had already been running Green Mountain (Nasdaq: GMCR), the coffee company he founded in Vermont, for two decades and was worth $89 million. At the time the soft-spoken, mellow CEO was already backing away from day-to-day business, meditating 45 minutes a day and espousing the virtues of "appreciative inquiry," a management technique developed at Case Western Reserve University that encourages people to learn from their successes instead of their mistakes.

Maybe he was too relaxed or too focused on the upside. Little more than a decade later, he may now lose it all for spending money that he didn't yet have in hand. As has been widely reported, he borrowed against his Green Mountain shares to fund an increasingly extravagant lifestyle. He told me last summer that he had pledged the shares long before the stock took off and he’d done so because for a long time he couldn’t, as an insider, sell any shares because of various lock-up periods tied to deals.

Borrowing against shares that are increasing in value works well but when those shares start to fall, things can unravel quickly, as has been the case with Stiller. Earlier this week he was forced to sell 5 million shares, or about 3.2% of shares outstanding, to cover margin calls on the loans. He was then removed as Chairman of the Board. Stiller, who still has a huge portion of his remaining shares pledged, is apparently saying he will fight to get his position back.

His story is a cautionary tale for other entrepreneurs who hold most of their fortunes in their public companies. Stiller debuted among the Forbes 400 list of richest Americans last year, after Green Mountain’s stock more than tripled in 12 months to $97. It is now trading at $26. At the time, nearly 90% of his fortune was held in that one stock and 5% in Krispy Kreme, in which he'd recently invested. (He also had to dump those shares this week).

Of the 1210 billionaires we found in March, 269 held 80% or more of their fortunes in public stocks including 43 Americans. Among them are people like Chip Wilson, the founder of yoga apparel phenom Lululemon, another high-flying stock that trades at 58 times earnings, and Robert Pera, who jumped into the ranks after his Ubiquiti Networks listed in November; the stock climbed steadily after going public, but has sunk 30% since mid-April. It fell 5% just today. (See www.forbes.com/real-time-billionaires). Facebook co-founders Mark Zuckerberg and Dustin Moskovitz will join this club of billionaires with concentrated public wealth next week.

Stiller is hardly the first person to borrow against his shares, though not many bet so much of the house. Some current examples include Forbes 400 real estate developer Steven Roth, Campbell Soup heir Bennett Dorrance and Ameritrade’s Joe Ricketts. Even Tesla's Elon Musk has a small number of shares pledged.

So what did Stiller buy with his borrowed money? Here is a tally of the assets he’s accumulated in recent years including a yacht, a $10 million Palm Beach house and a $17.5 million apartment he bought from New England Patriot’s quarterback Tom Brady. Nice toys but probably wasn't worth it.

Aviation business: 2004

A licensed pilot, he bought a small private air charter, Heritage Flight, in Burlington, VT., in 2004. It now has 10 aircraft, and provides aviation services such as maintenance, avionics, FBO, charter and aircraft management. Stiller told me last year that he’d used borrowed money to fund the venture and admitted the business probably wasn’t worth as much as he’d invested in it.

Yacht: 2007

Stiller retired as CEO of Green Mountain Coffee Roasters after 26 years. That same year he bought a 164-foot yacht Andale, which he re-christened as Grace E. Besides the name change, he apparently did a refit, changing all the furniture, adding WiFi and installing and IV system. He enclosing the sundeck, adding a gym on it. The yacht sleeps 14 guests; 11 crew members. I could not confirm how much he paid for the yacht or the refit but yachts of that size likely start around $25 million and cost approximately 10% a year of purchase price to operate. It is available for chartering for apparently a quarter of a million a week. Take a look here.